By CASEY MCNERTHNEY, SEATTLEPI.COM STAFF

Updated 10:00 pm, Tuesday, October 19, 2010

Police are investigating a Friday incident in which a man was knocked unconscious by another man outside a Pioneer Square nightclub.

About 1 a.m. Friday, police responded to the call about a man who was knocked down in a set of stairs and was bleeding from his head. The victim was on his back at the bottom of the stairs on the south side entrance to Heaven nightclub in the 100 block of South Washington Street, according to a police report.

"I saw a very large, deep, bloody gash on the left side of (the victim's) head," Officer Thomas Barnett wrote in the incident report. "His eyes were open slightly, and he was breathing, but he was not responsive."

Medics identified him by the identification in his back pocket.

A club security employee told police the victim was getting ready to climb the stairs when an unknown man walked behind him, put a "sleeper hold" around his neck and threw the victim to the ground. The suspect then walked back inside the club, police were told.

Officers reported several people went back into the club showing obvious intoxication. Barnett wrote that there was a strong odor of marijuana -- more than "just a couple of people inside and the residual smell from the clothing of persons who had smoked the marijuana outside."

Police said several unidentified patrons had identified the suspect as security staff member of the promoter. The club promoter told Barnett he had seen the suspect throughout the night but didn't know who he was and that the man was definitely not an employee of his. The promoter was cooperative, according to the report.

A woman at the club told police the suspect grabbed the man and threw him to the ground after he intervened in another disturbance.

No charges have been filed in the case. Police released only a vague suspect description. The victim regained consciousness, and his injuries were not considered life-threatening.